Scientists created a new type of pufferfish by mixing two kinds: the female obscure puffer and the male tiger puffer, which can live in fresh water and grow bigger than the obscure puffer.
The hybrid puffer had 38% more body weight at 4 and 6 months old compared to the obscure puffer.
They found special genes in the hybrid that help with growth and development, which might help improve breeding of pufferfish in the future.